The present invention relates to sealing of fluidic components, in particular in a high performance liquid chromatography application.
In high performance liquid chromatography (HPLC), a liquid has to be provided usually at a very controlled flow rate (e. g. in the range of microliters to milliliters per) and at high pressure (typically 20-100 MPa, 200-1000 bar, and beyond up to currently 200 MPa, 2000 bar) at which compressibility of the liquid becomes noticeable. For liquid separation in an HPLC system, a mobile phase comprising a sample fluid with compounds to be separated is driven through a stationary phase (such as a chromatographic column), thus separating different compounds of the sample fluid which may then be identified.
The mobile phase, for example a solvent, is pumped under high pressure typically through a column of packing medium (also referred to as packing material), and the sample (e.g. a chemical or biological mixture) to be analyzed is injected into the column. As the sample passes through the column with the liquid, the different compounds, each one having a different affinity for the packing medium, move through the column at different speeds. Those compounds having greater affinity for the packing medium move more slowly through the column than those having less affinity, and this speed differential results in the compounds being separated from one another as they pass through the column.
The mobile phase with the separated compounds exits the column and passes through a detector, which identifies the molecules, for example by spectrophotometric absorbance measurements. A two-dimensional plot of the detector measurements against elution time or volume, known as a chromatogram, may be made, and from the chromatogram the compounds may be identified. For each compound, the chromatogram displays a separate curve or “peak”. Effective separation of the compounds by the column is advantageous because it provides for measurements yielding well defined peaks having sharp maxima inflection points and narrow base widths, allowing excellent resolution and reliable identification of the mixture constituents. Broad peaks, caused by poor column performance, so called “Internal Band Broadening” or poor system performance, so called “External Band Broadening” are undesirable as they may allow minor components of the mixture to be masked by major components and go unidentified.
During operation, a flow of the mobile phase traverses the column filled with the stationary phase, and due to the physical interaction between the mobile and the stationary phase a separation of different compounds or components may be achieved. In case the mobile phase contains the sample fluid, the separation characteristics are usually adapted in order to separate compounds of such sample fluid. The term compound, as used herein, shall cover compounds which might comprise one or more different components. The stationary phase is subject to a mechanical force generated in particular by a hydraulic pump that pumps the mobile phase usually from an upstream connection of the column to a downstream connection of the column. As a result of flow, depending on the physical properties of the stationary phase and the mobile phase, a relatively high pressure occurs across the column.
The flow path of the mobile phase typically comprises plural individual components coupled together, which, in turn, might also be comprised of individual sub-components. Due to the high pressure applied in most HPLC application, pressure sealing of the components in and along the flow path is required. Further, in case of requirement of biocompatibility, it has to be ensured that all surfaces of components (including conduits) along the flow path that may come in contact with the mobile phase and the sample fluid are comprised of materials generally considered as being biocompatible, i.e., materials that will not release ions (e.g. from metal parts) that may contaminate the sample and/or a column packaging material, and/or adversely affect the analysis itself. Accordingly, proper sealing is required to ensure such biocompatibility.
EP 1910731 A1 discloses coupling of conduits for bringing them in communication. Each of the conduits is adapted for conducting a medium and has an outlet and an outer surface adjacent to the outlet. The outer surfaces and a solid plastic material are at least partly inserted into an aperture of a coupling element. The plastic material is plastified and/or melted at least partly. The plastic material is solidified for sealing and fixing the conduits within the aperture of the coupling element. The coupling element can be part of a flow cell configured for measuring an optical property of a fluid conducted through a fluid conduit.
GB 2422411 A discloses a fluidic terminal for placing one or more fluidic conduits in communication. A conduit for transporting fluid has a proximal end, a distal end, and a substantially cylindrical housing with an axial bore and a proximal face. The proximal end of the conduit is housed within the axial bore with their axes parallel, and the bore is back-filled with a thermoplastic polymer, most preferably PEEK, liquefied and cooled providing for the conduit to breach the sealing face and the thermoplastic to bond the conduit and housing.
Fittings for coupling different components, such as separation columns and conduits, of fluidic devices are commercially available and are offered, for instance, by the company Swagelok (see for instance the website swagelok.com). Typical fittings are disclosed in U.S. Pat. No. 5,074,599 A, U.S. Pat. No. 6,494,500, WO 2005/084337, WO 2009/088663 A1, US 2008/0237112 A1, or WO 2010/000324 A1.